Electrically conducting water-soluble self-doping polyaniline polymers and the aqueous solutions thereof

ABSTRACT

A self-doped conducting polymer having along its backbone a π-electron conjugated system which comprises a plurality of monomer units, between about 0.01 and 100 mole % of the units having covalently linked thereto at least one Bronsted acid group. The conductive zwitterionic polymer is also provided, as are monomers useful in the preparation of the polymer and electrodes comprising the polymer.

This is a continuation of U.S. Ser. No. 08/015,334, filed Feb. 8, 1993,now abandoned, which is a continuation of U.S. Ser. No. 07/616,743,filed on Nov. 16, 1990, now U.S. Pat. No. 5,310,781, which is acontinuation of U.S. Ser. No. 07/243,530, filed on Sep. 12, 1988, nowabandoned, which is a continuation-in-part of U.S. Ser. No. 07/156,928filed Dec. 14, 1987, now abandoned, which claims priority ofInternational Application PCT/US86/02042, filed on Sep. 29, 1986, whichclaims priority on Japanese Patent Application 64373/86 filed Mar. 24,1986.

FIELD OF THE INVENTION

This invention relates generally to the field of conducting polymers.More particularly the invention relates to self-doped conjugatedpolymers in which Bronsted acid groups are covalently bound to thebackbone of the polymer.

BACKGROUND

The requirements for conductive polymers used in the electronic andother industries are becoming more and more stringent. There is also anincreasing need for materials which permit reduction in the size andweight of electronic parts and which themselves exhibit long-termstability and superior performance.

In order to satisfy these demands, active efforts have been made inrecent years to develop new conductive macromolecular or polymericmaterials. A number of proposals have also been made regarding thepotential uses of such new compounds. For example, P. J. Nigrey et al.in Chem. Comm. pp. 591 et seq. (1979) have disclosed the use ofpolyacetylenes as secondary battery electrodes. Similarly, in the J.Electro Chem. Soc., p. 1651 et seq. (1980 and in Japanese PatentApplication Nos. 136469/1981, 121168/1981, 3870/1984, 3872/1984,3873/1984, 196566/1984, 196573/1984, 203368/1984, and 203369/1984, havealso disclosed the use of polyacetylenes, Schiff base-containingquinazone polymers, polyarylene quinones, poly-p-phenylenes,poly-2,5-thienylenes and other polymeric materials as electrodematerials for secondary batteries.

The use of polymeric materials in electrochromic applications has alsobeen suggested, in, e.g., A. F. Diaz et al., J. Electroanal. Chem. 111:111 et seg. (1980), Yoneyama et al., J. Electroanal. Chem. 161, p. 419(1984) (polyaniline), A. F. Diaz et al., J. Electroanal. Chem. 149: 101(1983) (polypyrrole), M. A. Druy et al., Journal de Physique 44: C3-595(June 1983), and Kaneto et al., Japan Journal of Applied Physics 22(7):L412 (1983) (polythiophene).

These highly-conductive polymers known in the art are typically renderedconductive through the process of doping with acceptors or donors. Inacceptor-doping, the backbone of the acceptor-doped polymer is oxidized,thereby introducing positive charges into the polymer chain. Similarly,in donor doping, the polymer is reduced, so that negative charges areintroduced into the polymer chain. It is these mobile positive ornegative charges which are externally introduced into the polymer chainsthat are responsible for the electrical conductivity of the dopedpolymers. In addition, such "p-type" (oxidation) or "n-type" (reduction)doping is responsible for substantially all the changes in electronicstructure which occur after doping, including, for example, changes inthe optical and infrared absorption spectra.

Thus, in all previous methods of doping the counterions are derived froman external acceptor or donor functionality. During electrochemicalcycling between neutral and ionic states, then, the counterions mustmigrate in and out of the bulk of the polymer. This solid statediffusion of externally introduced counterions is often therate-limiting step in the cycling process. It is thus desirable toovercome this limitation and thereby decrease the response time inelectrochemical or electrochromic doping and undoping operations. It hasbeen found that the response time can be shortened if the periodrequired for migration of counterions can be curtailed. The presentinvention is predicated upon this discovery.

SUMARRY OF THE INVENTION

The present invention provides conducting polymers that can be rapidlydoped and undoped, and which are capable of maintaining a stable, dopedstate for long periods of time relative to conducting polymers of theprior art. The superior properties of the polymers of the present-invention result from the discovery that conducting polmers can be madein a "self-doped" form; i.e., the counterion that provides conductivitycan be covalently linked to the polymer itself. In contrast to thepolymers of the prior art, therefore, the need for externally introducedcounterions is obviated, and the rate-limiting diffusion step alluded toabove is eliminated as well.

The polymers of the invention can display conductivities of on the orderof at least about 1 S/cm. The self-doped polymers may be used aselectrodes in electrochemical cells, as conductive layers inelectrochromic displays, field effective transistors, Schottky diodesand the like, or in any number of applications where a highly conductivepolymer which exhibits rapid doping kinetics is desirable.

In its broadest aspect, the present invention is directed to aconducting self-doped polymer having along its backbone a p-electronconjugated system which comprises a plurality of monomer units, betweenabout 0.01 and 100 mole % of said units having covalently linked theretoat least one Bronsted acid group. The present invention also encompassesthe zwitterionic form of such polymers. Polymers which may form thebackbone of the compounds of the present invention include, for example,polypyrroles, polythiophenes, polyisothianaphthenes, polyanilines,poly-p-phenylenes and copolymers thereof.

In a preferred embodiment, self-doped polymers described above have arecurring structure selected from the following structures (I), (II) or(III): ##STR1## wherein, in Formula I: Ht is a heterogroup; Y₁ isselected from the group consisting of hydrogen and --R--X--M; M is anatom or group which when oxidized yields a positive monovalentcounterion; X is a Bronsted acid anion; and R is a linear or branchedalkylene, ether, ester or amide moiety having between 1 and about 10carbon atoms. In Formulae II and III, Y₂, Y₃ and Y₄ are independentlyselected from the group consisting of hydrogen and --R--X--M, and R, Xand M are as given for Formula I.

A preferred subset of the poly(p-phenylenevinylenes) given by FormulaIII may be represented by structure III-1, as follows: ##STR2## InFormula III-1, M is as defined earlier, n is an integer in the range of1 to 10 inclusive, and R' is --(CH₂)_(n) SO₃ ⁻ M⁺, alkyl (1-10C), oraryl. In the latter case, R' is typically monocyclic, and may or may notbe substituted with one or more alkyl (1-10C) groups.

In yet another preferred embodiment of the invention, a conductivepolymer is provided containing a recurring zwitterionic structureaccording to (Ia), (IIa) or (IIIa): ##STR3## wherein Ht, R and X are asdefined above.

The invention is also directed to monomers useful in making the aboveself-doped polymers, methods of synthesizing the polymers, and devicesemploying the polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared spectrum of poly(methylthiophene-3-(2ethanesulfonate);

FIG. 2 is an infrared spectrum of poly(thiophene-3-(2-ethanesulfonicacid sodium salt));

FIG. 3 is an infrared spectrum of poly(methylthiophene-3-(4-butanesulfonate));

FIG. 4 is an infrared spectrum of poly(thiophene-3-(4-butanesulfonicacid sodium salt));

FIG. 5 depicts a series of vis-near ir spectra ofpoly(thiophene-3-(4-butanesulfonic acid sodium salt));

FIG. 6 depicts a series of vis-near ir spectra ofpoly(thiophene-3-(4-butanesulfonic acid sodium salt));

FIG. 7 depicts a series of vis-near ir spectre of poly(methylthiophene-3-(4-butanesulfonate));

FIG. 8 illustrates the results of cyclic voltammetry carried out onfilms of poly(thiophene-3-(2-ethanesulfonic acid)); and

FIG. 9 depicts a series of vis-near ir spectra ofpoly(thiophene-3-(2-ethanesulfonic acid)).

DETAILED DESCRIPTION

The terms "conducting" or "conductive" indicate the ability to transmitelectric charge by the passage of ionized atoms or electrons."Conducting" or "conductive" compounds include compounds which embody orincorporate mobile ions or electrons as well as compounds which may beoxidized so as to embody or incorporate mobile ions or electrons.

The term "self-doping" means that a material may be rendered conductingor conductive without external introduction of ions by conventionaldoping techniques. In the self-doping polymers disclosed herein,potential counterions are covalently bound to the polymer backbone.

The term "Bronsted acid" is used to refer to a chemical species whichcan act as a source of one or more protons, i.e. as a proton-donor. See,e.g., the McGraw-Hill Dictionary of Scientific and Technical Terms (3rdEd. 1984) at page 220. Examples of Bronsted acids thus includecarboxylic, sulfonic and phosphoric acids.

The term "Bronsted acid group" as used herein means Bronsted acids asdefined above, anions of Bronsted acids (i.e. where the protons havebeen removed), and salts of Bronsted acids, in which a Bronsted acidanion is associated with a monovalent cationic counterion.

"Monomer units" as used herein refer to the recurring structural unitsof a polymer. The individual monomer units of a particular polymer maybe identical, as in a homopolymer, or different, as in a copolymer.

The polymers of the present invention, which may be copolymers orhomopolymets, have a backbone structure that provides a p-electronconjugated system. Examples of such polymer backbones include, but arenot limited to, polypyrroles, polythiophenes, polyisothianaphthenes,polyanilines, poly-p-phenylenes and copolymers thereof. The recurringstructure described above may constitute anywhere from about 0.01 toabout 100 mole % monomers substituted with one or more "--R--X--M"functionalities. In applications requiring high conductivity, usually atleast about 10 mole % of the monomer units are substituted, typicallyabout 50 to 100 mole %. In semiconductor applications, it is usuallyless than about 10 mole % of the monomer units that are substituted,sometimes as little as about 0.1 or about 0.01 mole %.

Polyheterocycle monomer units represented by Formulae I and Ia includemonomer units which are either mono-substituted or di-substituted withthe --R--X--M functionality. Similarly, the polyaniline monomer unitsrepresented by Formulae II and IIa and the poly(p-phenylenevinylene)monomer units represented by Formulae III and IIIa include monomer unitswhich are substituted with 1, 2, 3 or 4 "--R--X--M" substitutents.Copolymers encompassing these different types of substituted monomerunits are envisioned by the present invention as well. In both thehomopolymers and copolymers of the present invention, between about0.01% and 100 mole % of the polymer should be provided with Bronstedacid groups.

In a preferred embodiment, the present invention encompasseselectrically neutral polymers given by Formulae I, II or III above. Inorder to render the polymers conductive, they must be oxidized so as toremove the M moiety and yield a polymer containing a recurringzwitterionlic structure according to Ia, IIa or IIIa. In the preferredembodiment, for example, Ht may be selected from the group consisting ofNH, S, O, Se and Te; M may be H, Na, Li or K; X may be CO₂, SO₃ or HPO₃; and R is a straight chain alkylene or ether group (i.e., --(CH₂)_(x)-- or --(CH₂)_(y) O(CH₂)_(z) --, where x and (y+z) are from 1 to about10). In a particularly preferred embodiment, Ht is NH or S; M is H, Lior Na; X is CO₂ or SO₃ ; R is a linear alkylene having from 2 to about 4carbon atoms; and the substituted monomer units of the polymers areeither-mono- or di-substituted with --R--X--M groups.

In order to "undope" the zwitterionic form of the polymers, an electriccharge may be supplied in the direction contrary to that used in doping(alternatively, a mild reducing agent may be used as discussed below).The M moiety is caused to migrate into the polymer and neutralize the X⁻counterion. The undoping process is thus as rapid as the doping process.

Schemes I, II and III represent the oxidation and reduction of the abovepolymers (the mono-substituted embodiment is illustrated), i.e. thetransition between the electrically neutral and conductive zwitterionicforms: ##STR4## Where X is CO₂, the above electrochemical conversion isstrongly pH-dependent in the pH range of 1-6 (the pK_(a) for X=CO₂ andX=H in Formula I is about 5). Where X is SO₃, on the other hand, theabove electrochemical reaction is pH-independent over the much larger pHrange of about 1-14 (the pK_(a) for X=SO₃ and M=H in Formulae II and IIIis about 1). The sulfonic acid derivative is thus charged at virtuallyany pH, while the carboxylic acid derivative is charged at only lowerhydrogen ion concentration. By varying the pH of the polymer solution,then, it is easier to control the conductivity of the carboxylic acidderivatives than that of the corresponding sulfonic acid derivatives.The particular Bronsted acid moiety selected will thus depend on theparticular application.

These self-doped polymers have conductivities of at least about 1 S/cm(see Example 14) and typically have chain lengths of about severalhundred monomer units. Typically, chain lengths range from about 100 toabout 500 monomer units; higher molecular weights are preferred.

In the practice of the present invention, a Bronsted acid group isintroduced into a polymer to make it self-doping. The Bronsted acid maybe introduced into a monomer, followed by polymerization orcopolymerization. One may also prepare a polymer or copolymer of theunsubstituted monomers of Formulae I or II and then introduce theBronsted acid into the polymer backbone.

Covalently linking a Bronsted acid to a monomer or polymer is within theskill of the art. See, e.g., J. Am. Chem. Soc. 70:1556 (1948). By way ofillustration, an alkyl group on a monomer or polymer backbone can beconcatenated to an alkyl halide using N-bromo succinamide (NBS) as shownin Scheme IV: ##STR5## The halide can then be treated with sodiumcyanide/sodium hydroxide or sodium sulfite followed by hydrolysis togive a carboxylic or sulfonic Bronsted acid, respectively, as shown inScheme V: ##STR6## Another.example showing the addition of a Bronstedacid with an ether linking group is shown in Scheme VI: ##STR7##

Syntheses of various monomers useful in the practice of the presentinvention are set forth in Examples 1 through 12, below.

The polymers of the present invention may be synthesized by theelectrochemical methods set forth in, e.g., S. Hotta et al., Synth.Metals 9:381 (1984), or by chemical coupling methods such as thosedescribed in Wudl et al., J. Org. Chem. 49:3382 (1984), Wudl et al.,Mol. Cryst. Lig. Cryst. 118:199 (1985) and M. Kobayashi et al., Synth.Metals. 9:77 (1984).

When synthesized by electrochemical methods (i.e., anodically), thepolymeric zwitterions are produced directly. With the chemical couplingmethods, the neutral polymers result. The preferred synthetic method iselectrochemical, and is exemplified below by the production of asubstituted polyheterocyclic species.

A solution containing the monomer IV. ##STR8## with Ht, Y₁, R, X and Mas given above, is provided in a suitable solvent such as acetonitrile(particularly suitable for the sulfonic acid derivative, i.e. whereX=SO₃) along with an electrolyte such as tetrabutylammonium perchlorateor tetrabutylammonium fluoroborate. A working electrode of platinum,nickel, indium tin oxide (ITO)-coated glass or other suitable materialis provided, as is a counter electrode (cathode) of platinum oraluminum, preferably platinum. A current of between about 0.5 and 5mA/cm² is applied across the electrodes, and depending on the extent ofpolymerization desired (or the thickness of the polymeric film on asubstrate), the electropolymerization reaction is carried out forbetween a few minutes and a few hours. The temperature of thepolymerization reaction can range from about -30° C. to about 25° C.,but is preferably between about 5° C. and about 25° C.

Reduction of the zwitterionic polymer so produced to the neutral,undoped form may be effected by electrochemical reduction or bytreatment with any mild reducing agent, such as methanol or sodiumiodide in acetone. This process should be allowed to proceed for atleast several hours in order to ensure completion of the reaction.

The sulfonic acid monomer (X=SO₃) is polymerized as the alkylene esterhaving 1 to 2 carbon atoms, such as the methyl ester (see Examples 14and 15), while the carboxylic acid derivative (X=CO₂) may be prepared inits acid form. After polymerization of the sulfonic acid derivative, themethyl group is removed in the treatment with sodium iodide or the like.

The polyanilines represented by Formulae II and IIa may be synthesizedelectrochemically as above or they may be prepared by the reaction of aphenylenediamine with a suitably substituted cy clohexanedione. SchemeVII, below, illustrates this latter synthesis: ##STR9## R, X and M areas defined above.

The poly(p-phenylenevinylenes) of Formulae III and IIIa are synthesizedsomewhat differently: ##STR10##

Copolymerization of different types of monomers represented in FormulaeI, II or III may be effected according to the same procedures outlinedabove. In a preferred embodiment, the majority of monomers are at leastmono-substituted with an --R--X--M group as described

Composites of the polymers of Formulae I, II and III may be prepared inconjunction with water-soluble polymers such as polyvinyl alcohol (seeExample 17) and the polysaccharides. Because the polymers of the presentinvention may be fairly brittle, preparation of composites usingadditional polymeric materials provides polymers which are more flexibleand less brittle. Films may be cast from aqueous solutions of polymersgiven by Formulae I, II or III also containing a predetermined amount ofone or more additional water-soluble polymers. Since the key proceduralcriterion in this step is dissolving two or more polymers in water, theonly practical limitation on the additional polymers is that they bewater-soluble.

The polymers of the present invention offer a specific advantage overconventional conducting polymers for use as electrodes inelectrochemical cells. Because the counterions are covalently bound tothe polymer, the cell capacity is not limited by electrolyteconcentration and solubility. This means that in optimized cells, thetotal amount of electrolyte and solvent can be reduced considerably,thus enhancing the energy density of the resulting battery. The facilekinetics of ion transport provided by the novel self-doping mechanismleads to rapid charge and discharge as well as to faster electrochromicswitching. Electrodes fabricated using the polymers of the invention maybe fabricated entirely from these polymers or from conventionalsubstrates coated with these polymers. Conventional substrates mayinclude, for example, indium tin oxide coated glass, platinum, nickel,palladium or any other suitable anode materials. When used as anelectrode, the internal self-doping of the polymer effects thetransition represented by Scheme I.

The self-doped conducting polymers of the invention also offer specificadvantages over conventional conducting polymers for use in a variety ofdevice applications where long term performance requires that the dopantions not be continuously mobile. Examples of such uses includefabrication of Schottky diodes, field effective transistors, etc.Because the dopant ion is covalently bound to the polymer chain inself-doped polymers, the problem of diffusion of the ion (e.g., in thevicinity of a junction or interface) is solved.

EXAMPLES

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiment thereof,r that theforegoing description as well as the examples which follow are intendedto illustrate and not limit the scope of the claimed invention. Otheraspects, advantages and modifications within the scope of the inventionwill be apparent to those skilled in the art to which the inventionpertains.

Example 1 2-(3-Thienyl)-Ethyl Methanesulfonate

To a solution of 5.0 g (7.8×10⁻³ mol) of 2-(3-thienyl)-ethanol (AldrichChemical) in 10 ml of dry, freshly distilled pyridine was added 3.62 ml(1.2 equiv.) of methanesulfonyl chloride in 20 ml of pyridine at 5°-10°C. The addition was carried out gradually, over a period of about 15-20min. The reaction mixture was stirred overnight at room temperature andwas quenched by pouring into a separatory funnel containing water andether. The layers were separated and the aqueous layer was extractedthree times with ether. The combined organic extracts were extractedonce with 10% hydrochloric acid, followed by water and drying over Na₂SO₄. Evaporation of the solvent afforded 5.3 g of a light brown oil (65%yield), and tlc (CHCl₃) showed a single spot. Chromatographicpurification on silica gel afforded a light yellow oil. Nmr (CDCl₃, δrel TMS) 2.9s, 3H; 3.1t, 2H; 4.4t, 2H; 7.0-7.4m, 3H. Ir (neat, ν cm⁻¹)3100w, 2930w, 2920w 1415w, 1355s, 1335s, 1245w, 1173s, 1080w, 1055w,970s, 955s, 903m, 850m, 825w, 795s, 775s, 740w. MS, 206.0.

Example 2 2-(3-Thienyl)-Ethyl Iodide

The above methanesulfonate (5.3 g, 2.6×10⁻² mol) was added to a solutionof 7.7 g (2 equiv) of NaI in 30 ml of acetone and allowed to react atroom temperature for 24 hr. The CH₃ SO₃ Na which had precipitated wasseparated by filtration. The filtrate was poured into water, extractedwith chloroform, and the organic layer was dried over MgSO₄. Evaporationof the solvent afforded a light brown oil which upon chromatographicpurification gave 5.05 g of a light yellow oil (82.5%). Nmr (CDCl₃, δrel TMS): 3.2m, 4H; 7.0-7.4m, 3H. Ir (KBr, ν cm⁻¹): 3100m, 2960s, 2920s,2850w, 1760w, 1565w, 1535w, 1450m, 1428s, 1415s, 1390w, 1328w, 1305w,1255s, 1222m, 1170s, 1152m, 1100w, 1080m, 1020w, 940m, 900w, 857s, 840s,810w, 770s, 695s, 633m. MS 238.

Example 3 Sodium-2-(3-Thienyl)-Ethanesulfonate

To a 10 ml aqueous solution of 5.347 g (4.2×10⁻² mol) of Na₂ SO₃ wasadded 5.05 g (0.5 equiv) of the above iodide and the reaction mixturewas heated to 70° C. for 45 hr. The resulting mixture was evaporated todryness followed by washing with chloroform to remove the unreactediodide (0.45 g) and acetone to remove the sodium iodide. The remainingsolid was a mixture of the desired sodium salt contaminated with excesssodium sulfite and was used in subsequent steps without furtherpurification. Nmr (D₂ O, δ rel TMS propanesulfonate): 3.1s, 4H;7.0-7.4m, 3H. Ir (KBr, ν, cm⁻¹, Na₂ SO₃ peaks subtracted) 1272m, 1242s,1210s, 1177s, 1120m, 1056s, 760m, 678w.

Example 4 2-(3-Thienyl)-Ethanesulfonyl Chloride

To a stirred suspension of 2 g of the above mixture of salts prepared inExample 3 was added dropwise 2 ml of distilled thionyl chloride. Themixture was allowed to stir for 30 min. The white solid resulting fromice-water quench was separated by filtration and recrystallized fromchloroform-hexane to afford 800 mg of white crystals, mp 57°-58° C. Nmr(CDCl₃, δ rel TMS) 3.4m, 2H; 3.9m, 2H; 7.0-7.4m, 3H. Ir (KBr, ν cm⁻¹)3100w, 2980w, 2960w, 2930w, 1455w, 1412w, 1358s, 1278w, 1260w, 1225w,1165s, 1075w, 935w, 865m, 830m, 790s, 770w, 750m, 678s, 625m. El. Anal.Calcd. for C₆ H₇ ClO₂ S₂ : C, 34.20; H, 3.35; Cl, 16.83; S, 30.43.Found: C, 34.38, H, 3.32; Cl, 16.69; S, 30.24.

Example 5 Methyl 2-(3-Thienyl)-Ethanesulfonate (e.g. methylthiophene-3-(2-ethanesulfonate))

To a stirred solution of 105 mg (5×10⁻⁴ mol) of the above acid chloride(prepared in Example 4) in 1.5 ml of freshly distilled (from molecularsieves) methanol was added, at room temperature, 1.74 ml (2 equiv) ofN,N-diisopropylethylamine. The reaction mixture was stirred for 12 hrand then transferred to a separatory funnel containing dilute, aqueousHCl and was extracted with chloroform thrice. After the combined organiclayers were dried with Na₂ SO₄, the solvent was evaporated to afford alight brown oil which was purified by chromatography on silica gel withchloroform as eluent. The resulting colorless solid, obtained in 90%yield had an mp of 27°-28.5° C. Ir (neat film, ν cm⁻¹) 3100w, 2960w,2930w, 1450m, 1415w, 1355s, 1250w, 1165s, 985s, 840w, 820w, 780m, 630w,615w. Uv-vis λmax, MeOH, nm(ε)! 234 (6×10³). Nmr (CDCl₃, δ rel TMS)7.42-7.22q, 1H; 7.18-6.80m, 2H; 3.85s, 3H; 3.6-2.9m, 4H. El. Anal.Calcd. for C₇ H₁₀ O₃ S₂ : C, 40.76; H, 4.89; S, 31.08. Found: C, 40.90;H, 4.84; S, 30.92.

Example 6 Ethyl-2-Carboxyethyl-4-(3-Thienyl)-Butanoate

To a stirred solution of 11.2 g (69.94 mmol) of diethyl malonate in 60ml of freshly distilled DMF, was added 2.85 g (69.94 mmol) of a 60% oildispersion of NaH. After 30 min stirring, 15.86 g (66.61 mmol) of2-(3-thienyl)-ethyl-iodide (prepared as described above) in 20 ml of DMFwas added dropwise over 10 min. The reaction mixture was stirred at roomtemperature for one hr and then heated to 140° for four hr. Uponcooling, the reaction was poured into ice-dil. HCl and extracted sixtimes with ether. The combined organic layers were washed with water,dried with Na₂ SO₄ and evaporated to afford a brown oil. Afterchromatography on silica gel (50% hexane in chloroform), a colorless oilwas obtained in 98% yield. El. Anal. Calcd. for C₁₃ H₁₈ O₄ S: C, 57.76;H, 6.71; S, 11.86. Found: C, 57.65; H, 6.76; S, 11.77. Nmr (CDCl₃, δ relTMS) 7.40-7.20t, 1H; 7.10-6.86d, 2H, 4.18q, 4H; 3.33t, 1H; 2.97-1.97m,4H; 1.23t, 6H. Ir (neat film, ν cm⁻¹) 2980w, 1730s, 1450w, 1370w, 775w.

Example 7 2-Carboxy-4-(3-Thienyl)-Butanoic Acid

To a stirred solution of 1.4 g (24.96 mmol) of potassium hydroxide in7.0 ml of 50% ethanol in water, was added the above diester (765 mg,2.83 mmol) prepared in Example 6. The resulting reaction was allowed tostir at room temperature for two hr, followed by overnight reflux. Theresulting mixture was poured into ice-10% HCl, followed by three etherextractions. The combined organic layer was dired with Na₂ SO₄ andevaporated to afford a white solid in 90% which was recrystallized fromchloroform-hexane to produce colorless needles. Mp, 118°-119° C.; nmr(DMSO/d6, δ rel TMS) 12.60br s, 2H; 7.53-6.80m, 3H; 3.20t, 1H; 2.60t,2H; 1.99q, 2H. Ir (KBr, ν cm⁻¹) 2900w, 1710s, 1410w, 1260w, 925w, 780s.El. Anal. Calcd. for C₉ H₁₀ O₄ S: C, 56.45; H, 5.92; S, 18.83. Found: C,56.39; H, 5.92; S, 18.67.

Example 8 4-(3-Thienyl)-Butyl Methanesulfonate

4-(3-thienyl)-butanoic acid (CA 69:18565x, 72:121265k) was prepared bystandard thermal decarboxylation of the carboxy acid prepared in Example7. This compound was then reduced to give 4-(3-thienyl)-butanol (CA70:68035r, 72: 121265k) also using standard methods.

To a solution of 1.05 g (6.7×10⁻³ mol) of 4-(3-thienyl)-butanol in 25 mlof dry, freshly distilled pyridine was added 0.85 g (1.1 equiv.) ofmethane-sulfonyl chloride at 25° C. The addition was gradual and carriedout over a-several minute period. The reaction mixture was stirred for 6hr at room temperature and quenched by pouring into a separtory funnelcontaining water-HCl and ether. The layers were separated and theaqueous layer was extracted once with 10% hydrochloric acid, followed byextraction with water and drying with Na₂ SO₄ Evaporation of the solventafforded 1.51 g of a light brown oil (95% yield), tlc (CHCl₃) showed asingle spot. El. Anal. Calcd. for C₉ H₁₄ O₃ S₂ : C, 46.13; H, 6.02; S,27.36. Found: C, 45.92; H, 5.94; S, 27.15. Nmr (CDCl₃ δ rel TMS) 2.0-1.5brs, 4H; 2.67 brt, 2H; 2.97s, 3H; 4.22t, 2H; 7.07-6.80d, 2H; 7.37-7.13,1H.

Example 9 4-(3-Thienyl Butyl Iodide)

The above methanesulfonate (1.51 g, 6.4×10⁻³ mol) prepared in Example 8was added to a solution of 1.93 g (2 equiv.) of NaI in 14 ml of acetoneand allowed to react at room temperature overnight. The reaction mixturewas then heated to reflux for 5 hr. The CH₃ SO₃ Na which hadprecipitated was separated by filtration. The filtrate was poured intowater, extracted with chloroform and the organic layer was dried withMgSO₄. Evaporation of the solvent afforded a light brown oil which uponchromatographic purification (silica gel, 60% hexane in chloroform) gave1.34 g of a colorless oil (78%). Nmr (CDCl₃, δ rel to TMS) 1.53-2.20m,4H; 2.64t, 2H; 3.17t, 2H; 6.83-7.10d, 2H; 7.13-7.37t, 1H. Ir (KBr, νcm⁻¹) 2960s, 2905s, 2840s, 1760w, 1565w, 1535w, 1450s, 1428s, 1415s,1190s, 750s, 695m, 633m. MS 266.0. El. Anal. Calcd. for C₈ H₁₁ IS: C,36.10; H, 4.17; I, 47.68; S, 12.05. Found: C, 37.68; H, 4.35; I, 45.24;S. 12.00

Example 10 Sodium-4-(3-Thienyl)-Butanesulfonate

To a 2 ml aqueous solution of 1.271 g (1×10⁻² mol) of Na₂ SO₃ was added1.34 g (0.5 equiv) of the above iodide prepared in Example 9. Thereaction mixture was heated to reflux for 18 hr. The resulting mixturewas evaporated to dryness, followed by washing with chloroform to removethe unreacted iodide and with acetone to remove the sodium iodide. Theremaining solid was a mixture of the desired sodium salt contaminatedwith excess sodium sulfite and was used in subsequent steps withoutfurther purification. Nmr (D₂ O, δ rel TMS propane-sufonate) 1.53-1.97m,4H; 2.47-3.13m, 4H; 6.97-7.20d, 2H; 7.30-7.50q, 1H. Ir (KBr, ν cm⁻¹, Na₂SO₃ peaks subtracted) 2905w, 1280m, 1210s, 1180s, 1242m, 1210s, 1180s,1130s, 1060s, 970s, 770s, 690w, 630s, 605s.

Example 11 4-(3-Thienyl)-Butanesulfonyl Chloride

To a stirred suspension of 1.00 g of the above mixture of salts (fromExample 10) in 10 ml of freshly distilled DMF was added dropwise 1.43 gof distilled thionyl chloride. The mixture was allowed to stir for 3 hr.The slighly yellow oil resulting from ice-water quench was isolated bytwice extracting with ether, followed by drying of the organic layerwith Na₂ SO₄ to yield 566 mg of a slightly yellow oil which crystallizedslowly (mp 26°-27°) after chromatography (silica gel, chloroform). Nmr(CDCl₃, δ rel TMS) 1.45-2.38m, 4H; 2.72t, 2H; 3.65t, 2H; 6.78-7.12d, 2H;7.18-7.42, 1H. Ir (neat film, ν cm⁻¹) 3120w, 2920s, 2870m, 1465m, 1370s,1278w, 1260w, 1160s, 1075w, 935w, 850w, 830m, 7763s, 680m, 625w, 585s,535s, 510s. El. Anal. Calcd. for C₈ H₁₁ ClO₂ S₂ : C, 40.25; H, 4.64; Cl,14.85; S, 26.86. Found: C, 40.23; H, 4.69; Cl, 14.94; S, 26.68.

Example 12 Methyl 4-(3-Thienyl)-Butanesulfonate (e.g. methylthiophene-3-(4-butanesulfonate)

To a stirred solution of 362 mg (1.5×10⁻³ mol) of the above acidchloride prepared in Example 11 in 6 ml of freshly distilled (frommolecular sieves) methanol was added, at room temperature, 392 mg (2equiv) of N,N-diisopropylethylamine. The reaction mixture was stirredfor 2 hr and then transferred to a separatory funnel containing dilute,aqueous HCl and was extracted with chloroform thrice. After the combinedorganic layers were dried with Na₂ SO₄, the solvent was evaporated toafford a light brown oil which was purified by chromatography on silicagel with 40% hexane in chloroform as eluent. The resulting colorlessoil, obtained in 84% yield had the following properties: El. Anal.Calcd. for C₉ H₁₄ S₂ O₃ : C, 46.13; H, 6.02; S, 27.36. Found: C, 45.97;H, 5.98; S, 27.28. Ir (neat film, ν, cm⁻¹) 3100w, 2970m, 2860w, 1460m,1410w, 1350s, 1250w, 1160s, 982s, 830m, 800m, 770s, 710w, 690w, 630w,613w, 570m. Uv-vis λmax, MeOH, nm (ε)! 220 (6.6×10³). Nmr (CDCl₃, δ relto TMS) 7.33-7.13 (t, 1H), 7.03-6.77 (d, 2H), 3.83 (s, 3H), 3.09 (t,2H), 2.67 (t,2 H), 2.2-1.5 (m, 4H).

Example 13 Polymerization of ThioPhene-3-Acetic Acid ##STR11##

Thiophene-3-acetic acid (Formula V) was polymerized at room temperatureby the electrochemical polymerization method of S. Hotta et al., Synth.Metals, supra, using acetonitrile as the solvent and LiClO₄ as theelectrolyte. Blue-black films were produced, indicating formation of thezwitterionic polymer of Formula Ia (Y₁ =H, R=--CH₂ --, Ht=S, X=CO₂). Thepolymer films were electrochemically cycled and observed to undergo acolor change from blue-black to yellowish brown, indicating reduction ofthe zwitterionic form of the polymer to the neutral form represented byFormula I. The infrared spectrum was in agreement with the proposedstructure.

Example 14 Poly(Thiophene-3-(2-Ethanesulfonic Acid Sodium Salt))##STR12##

Methyl thiophene-3-(2-ethanesulfonate) (Formula VI) was prepared asabove. Polymerization of the above monomer was carried out as in Example13, except that the polymerization temperature was maintained at -27° C.The resultant polymer ("methyl P3-ETS", Formula VII) was then treatedwith sodium iodide in acetone to remove the methyl group from thesulfonic acid functionality and produce, in quantitative yield (˜98%),the corresponding sodium salt of the polymer, i.e. ofpoly(thiophene-3-(2-ethanesulfonic acid)) ("P3-ETSNa") as shown inFormula VIII. The polymeric methyl ester and the polymeric sodium saltwere characterized by infrared and ultraviolet spectroscopy as well asby elemental analysis (see FIGS. 1 and 2). The sodium salt was found tobe soluble in all proportions in water, enabling the casting of filmsfrom aqueous solution.

Electrochemical cells were constructed in glass to demonstrateelectrochemical doping and charge storage via in situoptoelectrochemical spectroscopy. The cells included a film of the abovepolymer on ITO-coated glass (which served as the anode), a platinumcounterelectrode (cathode) and a silver/silver chloride referenceelectrode with tetrabutylammonium perchlorate as electrolyte. FIG. 5depicts a series of vis-near ir spectra of the P3-ETSNa taken with thecell charged to a series of successively higher open circuit voltages.The results were typical of conducting polymers in that the π-π*transition was depleted with a concomitant shift of oscillator strengthinto two characteristic infrared bands. The results of FIG. 5demonstrate both reversible charge storage and electrochromism.

The electrical conductivity was measured with the standard 4-probetechniques using a film of the polymer cast from water onto a glasssubstrate onto which gold contacts had been previously deposited, uponexposure to bromine vapor, the electrical conductivity of P3-ETSNa roseto .sup.˜ 1 S/cm.

Example 15 Poly(Thiophene-3-(4-Butanesulfonic Acid Sodium Salt))##STR13##

Methyl thiophene-3-(4-butanesulfonate) (Formula IX) was prepared asabove. Polymerization was carried out under conditions identical tothose set forth in Examples 13 and 14 above. The resultant polymer(designated "methyl P3-BTS", Formula X) was treated with sodium iodidein acetone to produce, in quantitative yield, the sodium salt ofpoly(thiophene)-3-(4-butanesulfonic acid) ("P3-BTSNa", Formula XI). Thepolymeric methyl ester (Formula X) and the corresponding sodium salt(Formula XI) were characterized spectroscopically (ir, uv-vis) and byelemental analysis. The sodium salt was discovered to be soluble in allproportions in water, enabling the casting of films from aqueoussolution.

Electrochemical cells were constructed as in Example 14 in order todemonstrate electrochemical doping and charge storage via in situoptoelectrochemical spectroscopy. FIGS. 6 and 7 depict a series ofvis-near ir spectra of the P3-BTSNa and methyl P3-BTS respectively,taken with the cells charged to successively higher open circuitvoltages. As in Example 14, the results were found to be typical ofconducting polymers in that the π-π* transition was depleted with aconcomitant shift of oscillator strength into two characteristicinfrared bands. As in Example 14, the results of FIGS. 6 and 7demonstrate both reversible charge storage and electrochromism.

Example 16 Polymerization and Analysis ofPoly(Thiophene-3-(2-Ethanesulfonic Acid))

The polymeric sodium salt of thiophene-3-(2-ethanesulfonic acid)(Formula I, Ht=S, Y₁ =H, R=--CH₂ --, X=SO₃, M=H) was prepared asoutlined above, dissolved in water and subjected to ion exchangechromatography on the acid form of a cation exchange resin. The resultsof atomic absorption analysis of the dark red-brown effluent indicatedcomplete replacement of sodium by hydrogen. FIG. 8 shows the results ofcyclic voltammetry carried out on films of the polymer ("P3-ETSH"/ITOglass working electrode, platinum counterelectrode, and a silver/silverchloride reference electrode in acetonitrile with fluoroboricacid-trifluoroacetic acid as electrolyte). The figure indicates thatP3-ETSH is an electrochemically robust polymer when cycled between +0.1and +1.2 V versus silver/silver chloride in a strongly acidic medium.There are two closely spaced oxidation waves, the first of whichcorresponds to a change in color from orange to green. The polymer couldbe cycled and corresponding color changes observed without noticeablechange in stability at 100 mV/sec.

Electrochemical cells were constructed in glass to demonstrateelectrochemical doping and charge storage via in situoptoelectrochemical spectroscopy, substantially as in the previous twoExamples. The cells consisted of a film of the polymer on ITO glass(anode), platinum counterelectrode (cathode) and a silver/silverchloride reference electrode in acetonitrile with fluoroboricacid-trifluoroacetic acid as electrolyte.

FIG. 9 depicts a series of vis-near ir spectra of the P3-ETSH taken withthe cell charged, to a series of successively higher open circuitvoltages. In this case, the polymer was observed to spontaneously dopein the strongly acidic electrolyte solution. The results of FIG. 9demonstrate both reversible charge storage and electrochromism. Controlof the self-doping level for brief periods of time was achieved byimposing a voltage lower than the equilibrium circuit voltage.

Example 17 Preparation of Polymer Composite

Poly(thiophene-3-(2-ethanesulfonic acid)), (Formula I, Ht=S, Y₁ =H,R=--CH₂ CH₂ --, X=SO₃, M=H, "P3-ETSH") as prepared in Example 16 wasused to prepare a composite as follows. The compound was admixed with asolution of polyvinyl alcohol in water, and films of the neutral polymerwere cast. Free standing deep orange films (indicating chargeneutrality, as opposed to the blue-black zwitterionic polymers) castfrom the prepared solution had excellent mechanical properties (soft,smooth and flexible) and could be chemically doped and undoped bycompensation. This method of making conducting polymer composites isbroadly applicable to the use of any water-soluble polymer inconjunction with P3-ETSH or P3-BTSH.

Example 18 Preparation of Polymer of2,5-Diethoxycarbonyl-1,4-Cyclohexanedione and p-Phenylenediamine

To a suspension of 8.51 g (33.21 mmole) of2,5-diethoxycarbonyl-1,4-cyclohexanedione in 380 ml of freshly distilledbutanol was added 3.59 g of p-phenylenediamine in 20 ml of butanol,followed by 40 ml of glacial acetic acid. The resulting mixture washeated to reflux for a period of 36 hrs, then it was exposed to oxygenby refluxing over a period of-twelve hours, was hot filtered, the solidwas washed with ether and extracted in a Soxhlet extractor with thefollowing solvents: chloroform (6 days), chlorobenzene (5 days), andether (4 days). This treatment afforded a dark solid (8.42 g). Elementalanalysis calcd. for C₁₈ H₁₈ N₂ O₄ : C, 65.84; H, 6.14; N, 8.53. Found:C, 65.55; H, 6.21; N, 8.70. Ir (KBr, ν cm-¹) 3350w, 3240w, 2980m, 2900w,1650s, 1600s, 1510s, 1440m, 1400w, 1220s, 1090w, 1065s, 820w, 770m,600w, 495w.

Example 19 Polyaniline Dicarboxylic Acid

The above polymer diester is suspended in DMF and treated with asolution of 50% (w/w) sodium hydroxide. The reaction mixture is thenheated to 100° C. for 48 hr under strictly anaerobic conditions toexclude oxygen. Upon cooling the mixture, it is poured into ice/HCl andfiltered. The infrared spectrum of the product should show the followingcharacteristic absorption peaks: 3100-2900br, 1600s, 1500s, 1210s.

The following examples are directed to the synthesis of apoly(p-phenylenevinylene) (PPV) according to Scheme IX: ##STR14##

Example 20 Synthesis of a Poly(p-Phenylenevinylene)

Synthesis of (A):

To 200 ml of absolute ethanol was added 10.5 g sodium pellets at roomtemperature (RT). After the sodium was completely consumed, a solutionof 22.32 g 4-methoxyphenol in 80 ml of absolute ethanol was added. Theresulting solution was stirred for 10 min, then treated with 25.2 ml of3-chloropropanol. The mixture was refluxed for 16 hr, the solvent wasremoved in vacuum, and the residue was taken up in 200 ml of ether.After titration over charcoal, the titrate was concentrated to about 25ml. A large amount of white solid crystallized out to give 21.5 g IR(KBr, cm⁻¹) 3306, 3050, 2960, 2940, 2880, 2840, 1520, 1480, 1450, 1400,1300, 1245, 1185, 1065, 1040, 950, 830, 730. ¹ H NMR (CD₃ OD, δ rel toTMS): 1.6-2.0 (Q,2H), 3.5-4.0 (M,7H) 6.7 (S,4H). MS(EI,%): 182(M,41),124(100), 109(61).

Synthesis of (B):

To a solution of 5.10 g 3-(methoxyphenoxyl)propanol(A) in 20 ml offreshly distilled pyridine was added 3.26 ml of methanesulfonyl chloridein 5 ml pyridine. The reaction mixture was stirred at RT overnight andthen poured into a separatory funnel containing 80 ml of water and 80 mlof ether. The layers were separated and the aqueous layer was extractedtwice with 40 ml ether each time. The combined organic layers wereextracted twice with 40 ml of 10% hydrochloric acid followed by rinsingtwice with 40 ml H₂ O and drying with sodium sulfate for two hr. Afterevaporation of the solvent, a light brown oil was obtained which uponpassing through a 16×2.5 cm silica gel column using CHCl₃ as eluent gave6.04 g light yellow oil (65%). IR (KBr, cm⁻¹): 3020, 2960, 2940, 2880,2840, 1600, 1510, 1470, 1450, 1360, 1300, 1240, 1180, 1110, 1060, 980,950, 830. ¹ H NMR (CDCl₃, δ rel to TMS): 2.0-2.4 (Q,2H), 3.1 (S,3H), 3.8(S,3H), 3.9-4.2 (T,2H), 4.3-4.6 (T,2H), 6.8 (S,4H).

Synthesis of (C):

To a solution of 6.75 g of Nal in 100 ml of acetone was added 3.9 g (B).The mixture was allowed to react at RT for 24 hr. The CH₃ SO₃ Na, whichhad precipitated, was separated by filtration. The filtrate was pouredinto water extracted with chloroform and the organic layer was driedwith MgSO₄. Evaporation of the solvent afforded 4.073 g of product (93%)which upon passing through an 18×2.5 cm silica gel column using hexaneas eluent gave 3.20 g of dark-red liquid (73%). IR (KBr, cm⁻¹): 3020,3000, 2950, 2870, 2820, 1600, 1510, 1470, 1450, 1390, 1300, 1230, 1180,1110, 1040, 830, 740. ¹ H NMR (CDCl₃, δ rel to TMS): 2.1-2.4 (M,2H) ,3.2-3.5 (T,2H), 3.7-4.1 (M,5H), 6.8 (S,4H). MS(EI,%), 292 (M,25),202(15), 200(39), 124(100), 123(71), 109(61), 95 (25), 81(11), 77(11),64(11), 63(13), 52(12).

Synthesis of (D):

To 80 ml of an aqueous solution of 15.36 g of Na₂ SO₃ was added 17.8 gof (C) and the reaction mixture was heated to 70° C. for 85 hr. Theresulting solution was extracted with CHCl₃ to remove unreacted iodide(1.98 g). The aqueous layer was distilled in a rotary evaporator toremove water. The residue was washed with anhydrous acetone to removesodium iodide. The remaining solid was then dissolved in 600 ml of waterand passed through Amberlite IR-120 (plus) ion-exchange resin. Thesolution was concentrated to 200 ml in vacuum at 80° C. and wasneutralized by 0.5N NaOH solution. After evaporation of the solvent,12.8 g of grey-white solid was obtained (88%). IR (KBr, cm⁻¹): 3020,2960, 2920, 2880, 2840, 1520, 1480, 1450, 1300, 1250, 1230, 1200, 1120,1070, 1040, 830, 740, 640. ¹ H NMR (D₂ O, d rel to DSS): 2.1-2.4 (Q,2H),2.9-3.3 (T,2H), 3.8 (S,3H), 4.0-4.2 (T,2H), 7.0 (S,4H).

Synthesis of (E):

To a stirred suspension of 20.5 g of (D) in 80 ml of DMF was addeddropwise 20 ml of thionyl chloride, and the mixture was allowed to stirfor 45 min. The mixture was then quenched with 400 ml of ice water andextracted with 300 ml of ether. The ether layer was washed twice with200 ml of cold water, then the ether layer was dried with MgSO₄.Evaporation of solvent afforded 13.3 g of yellow solid product. IR (KBr,cm⁻¹): 3050, 2950, 2880, 2840, 1600, 1510, 1480, 1450, 1380, 1300, 1240,1170, 1110, 1050, 930, 830, 750, 730, 700. ¹ H NMR (CDCl₃, δ rel toTMS): 2.2-2.6 (M,2H), 3.8-4.3 (M,7H), 6.9 (S,4H). MS(EI,%), 266 (M⁺+2,16), 265 (M⁺ +1,5), 264 (M⁺,40), 143(20), 141(54), 137(20), 124(59),123(100, 109(44), 95(23).

Synthesis of (F):

To 150 ml of 37% formaldehyde aqueous solution was added 100 ml ofconcentrated hydrochloric acid at 0° C. The mixture was saturated withhydrogen chloride gas for 15 min before addition of 15 g of the abovesulfonyl chloride (E) in 80 ml of dioxane. The resulting mixture wasallowed to stir at room temperature for 3 hr. The white solid whichformed was collected by filtration and was recrystallized from benzeneto give 17.4 g white product (92%). Anal. calc'd for (C₁₂ H₁₅ Cl₃ O₄ S):C 39.83; H 4.15. Found: C 40.01; H 4.15. IR (KBr, cm⁻¹): 3060, 3000,2980, 2940, 2880, 2840, 1520, 1470, 1420, 1400, 1360, 1320, 1270, 1240,1160, 1070, 1050, 1030, 940, 920, 870, 800, 730, 690, 600. ¹ H NMR(CDCl₃, d rel to TMS): 2.4-2.8 (Q,2H)t 3.8-4.3 (M,7H), 4.6 (S,4H), 7.3(S,2H).

Synthesis of (G):

To 922 mg (F) in 10 ml of acetone and 10 ml of methanol was added 2 mlof dimethylsulfide. The mixture was stirred at room temperature for twodays under nitrogen. After the solvent was removed, the residue wasprecipitated with acetone and dried in vacuum to afford (G) inquantitative yield. IR (KBr, cm⁻¹): 3000, 2910, 2840, 1510, 1470, 1425,1400, 1320, 1230, 1190, 1150, 1040, 940, 900, 870, 730, 700, 600. ¹ HNMR (CD₃ OD, rel to TMS): 2.3-2.6 (M,2H), 3.0 (S,12H), 3.9-4.4 (M,7H),4.8 (S,4H, 7.3 (S,2H).

Polymerization of (G):

Method 1.

To a solution of monomer (G) (1.075, 2mmol) in 5 ml of MeOH was added0.48 ml of 25% NaOMe in MeOH at 0° C. under nitrogen. A viscous gum wasformed immediately. After a reaction time of 0.5 hr, the solvent wasdecanted and 8 ml of water and 2 ml of DMF were added. The resultingmixture was heated to reflux for half an hour to give a clearyellow-greenish solution. The solution was dialyzed against deionizedwater with Spectropore membrane tubing for 24 hr to give the desiredaqueous solution of precursor polymer (L) with pH value around 4.5. Theprecursor polymer (L) can be cast into films from aqueous solution. UV(film, λmax): 370. IR (film, ν cm⁻¹): 3450 (H₂ O), 3080, 3010, 2950,2880, 1650, 1510, 1470, 1330, 1210(broad), 1045, 940, 880, 800, 730,690, 610, 530.

Method 2.

Monomer (G) can also be polymerized by sodium hydroxide in water undersimilar conditions. But in the case of sodium hydroxide, one obtains aslightly viscous, milky solution instead of gum. This milky solutionbecame clear after refluxing with a small amount of DMF. Upon waterdialysis, the aqueous solution of the precursor polymer was obtainedwith the same UV and IR spectra as the above.

Conversion of (L) into PPV:

There are three ways to convert the precursor polymer (L) into fullyconjugated PPV:

Method 1.

The precursor polymer (L) was cast into films from aqueous solution. Thefilms then were heated to 200° C. and maintained at this temperature for4 hr in vacuo to yield an insoluble and infusible black film withbrilliant appearance. UV (λmax, nm): 490. IR (ν cm⁻¹): 4000-2000 (broaddispersion), 1610, 1520s, 1410, 1350, 1210 (broad), 1040s, 960, 850,800, 750, 600. Conductivity: σ(300K, air)=2×10⁻⁶ S cm⁻¹.

Method 2.

The aqueous solution of the precursor polymer (L) (10 ml) was mixed with10 ml of ethylene glycol. The mixture was heated to the boiling point.After all the water was removed, the temperature of the solution wasincreased to 190° C. and the solution turned red. The solution wasmaintained at reflux for 6 hr under nitrogen, then cooled and dialyzedagainst deionized water for 24 hr to afford a red aqueous solution ofsubstituted PPV from which a hygroscopic black film can be cast on aplastic weighing bowl at 45° C. in vacuo.

Method 3.

The aqueous solution of the precursor polymer (L) was mixed with thesame volume of DMF and excess of sodium methoxide. The mixture washeated to reflux for 4 hr to yield a red solution. After water dialysis,a red aqueous solution of substituted PPV was obtained.

The polymers obtained from methods 2 and 3 have the same UV and IRspectra as that from Method 3, but have higher conductivity ranging from10⁻⁴ -10² S cm⁻¹ which is humidity dependent.

We claim:
 1. A conducting water-soluble, self-doped polymer having alongits backbone a II-electrone conjugated system which comprises about 100to 500 monomer units, wherein about 0.01 and 100 mole % of the unitshave the following chemical formula ##STR15## wherein Y₂ and Y₃ arehydrogen, and Y₄ is selected from the group consisting of hydrogen and--R_(n) --X--M, wherein R is a direct bond when n is 0,X is SO₃ ; M isselected from H, Na, K, or Li; and n is 0, wherein said polymer isconductive without added external dopant when the moiety M is removed.2. The polymer of claim 1, wherein M is selected from the groupconsisting of H, Na, Li or K, and Y₄ is hydrogen.
 3. The polymer ofclaim 2 wherein M is Na.
 4. The polymer of claim 1, wherein M is H. 5.The polymer of claim 1, wherein M is Na.
 6. The polymer of claim 1wherein M is Li.
 7. The polymer of claim 1, wherein M is K.
 8. Anaqueous solution useful for casting conducting polymeric films, whichsolution comprises:(a) a water-soluble self-doped polymer comprisingabout 100 to 500 monomer units, wherein about 0.01 to 100 mole % of themonomer units have the chemical formula ##STR16## wherein Y₂ and Y₃ arehydrogen and Y₄ is selected from the group consisting of hydrogen and--R_(n) --X--M wherein R is a direct bond when n is 0, X is SO₃, M is H,Na, K, or Li, and n is 0, wherein said polymer is conductive withoutadded external dopant when the moiety M is removed; and (b) an amount ofwater at least sufficient to dissolve the polymer of part (a).
 9. Theaqueous solution of claim 8, wherein M is selected from the groupconsisting of H, Na, Li or K, and Y₄, is hydrogen.
 10. The aqueoussolution of claim 9, wherein M is Na.
 11. The aqueous solution of claim8, wherein M is Na.
 12. The aqueous solution of claim 8, wherein M is K.13. The aqueous solution of claim 8, wherein M is H.
 14. The aqueoussolution of claim 8, wherein M is Li.